A vehicle travels half the distance l with speed v1 and the other half with speed v2, then its average speed is [NCERT Exemplar]

Time taken to travel first half distance, t1=l/2v1=l2v1Time taken to travel second half distance, t2=l2v2Total tIme = t1+1t2=l2v1+l2v2=l21v1+1v2We know that, vav = Average speed                              =  total distance  total time =ll21v1+1v2=2v1v2v1+v2